Rotary drill



Jan. 6, 1948. c. J. EssELlNG ROTARY DRILL Filed June 5, 1946 FIC-Ll Patented Jan. 6, 1948 ROTARY DRILL Cornelis J. Esseling, Haarlem, Netherlands, as-

signor to Werf Conrad' En StorkfHijsch N. V.

Haarlem, Netherlands Netherlands, a

company of the Application June 5, 1946, Serial No. 674,431

, In the Netherlands February 20,1942

section 1, rubro Law 69o-, August 8,1946 Patent expires February 20, 1962 1 Claim. 1

This invention relates to drills of the type comprising in addition to a bit secured, through a line of drill rod, to a threaded rotary grief stem engaged by a nut adapted to be rotated by the stem at a speed differing from that of the stem f so that the stem is automatically screwed upward when the nut is arrested, a clutch provided in the transmission gear between the stem and the nut and adapted under the influence cf the descending stem automatically to be connected so as to turn the nut in accordance with the descending motion of the stem. In a known machine of this type, the nut is provided with an abutment for a spring, which encircles the stem and bears with its upper end against an abutment of a tensioning member, such as a handwheel, whose threaded hub is adapted to be screwed up and down in the stationary casing of nut and clutch.

This known construction is suitable for apparatus for drilling holes of comparatively small depths, since the nut and, consequently, the line of drill rod secured to the stem, is permanently loaded by the spring and cannot, as is desired with a View to ensuring uniform pressure on the bit in the drilling of relatively deep holes, be relieved from pressure at a rate proportionate to the increase of the length of the line of drill rod.

The present invention provides means for improving this known device in such manner that for said spring and tensioning member also serve for reducing the pressure n the bit as the drilling of the hole proceeds. In accordance with the invention, the nut is also provided with an abutment for the upper end, and the tensioning member is also provided with an abutment for the lower end of the spring, or of part thereof. If, in a device embodying this improvement, the tensioning member has been screwed down through a suicient distance, the lower end of the spring exerts downward pressure on the nut and the upper end thereof exerts upward pressure on an abutment of the tensioning member, i. e. the nut is loaded at a rate determined by the position of said member.

If, however, the tensioning member is screwed up, the upper end of the tensioned spring engages the upper abutment of the nut, the lower end thereof engaging an abutment of the tensioning member, so that the nut is relieved from pressure. In an intermediate position of the tensioning member, the nut is neither loaded nor unloaded, i. e. the pressure on the bit is determined exclusively by the weight of the line of drill rod and of the parts secured thereto.

In order that the invention may be more fully understood, reference` is had to' the annexed drawing, in which:

Fig. 1 is a vertical sectional View of a device in accordance with the invention and provided with one spring, and

Fig 2 is a similar view of the top portion of a device comprising two springs.

In the drawing, I is the drilling rod, 2 is the bit, 3 is the grief stem and 4 is the drilling head. Stem 3 has a longitudinal groove cooperating with a key 6 in a sleeve 1, so as to have freedom of vertical movement in said sleeve but to be prevented from rotation relative thereto. Secured to sleeve 1 is a mitre wheel 8, by mean-s of which it can be rotated in bearings 9 and Ill of the stationary casing II.

The stem 3 has a threaded top portion I2 cooperating with a nut I3, which can be urged downward by a coiled spring I4 encircling stem 3 and adapted to be tensioned by a handwheel I5, whose hub I6 is in threaded engagement with casing I I.

Also secured to sleeve l is a gear wheel I8 meshing with a stepped pinion I 9, which is rotatably mounted about a pivot 2U of casing II and meshes with a second gear wheel 2I, which is loosely mounted on sleeve 'I and whose diameter is slightly smaller than that of gear I8. Gear wheel 2l is provided on its top face with a friction ring '22 cooperating with a friction ring 23 secured to the bottom face of nut I3.

Countersunk in nut I3 is a slip ring 25 having two diametrically opposed studs 26 engaged by the bifurcated end 21 of a pivotally mounted, weighted hand lever (not shown), by means of which a conical face of nut I3 can be raised into engagement with a mating face of casing I I'.

If bit 2 turns in counterclockwise direction as indicated by arrow 24, screw I2 should be righthanded. Rotation of stem 3 is transmitted, through sleeve 1, gear wheel I8 and pinion I9, to gear wheel 2l which thus rotates at a slightly greater angular speed than stem 3. As long as the clutch constituted by the friction rings 22 and 23 is disconnected, nut I3 will rotate at the same speed as stem 3, since the frictional resistance of thread I2 exceeds that of ball bearing I'I. When, however, bit 2, together with stem 3 and nut I3, has sunk through a small distance, the said rings exert suflicient pressure on one another to cause nut I3 to follow the rotation of gear 2| i. e. to rotate at a'speed slightly exceeding that of stem 3, so that it is screwed up and spring I4 again exerts its full pressure on the stem, until the clutch, owing to a further descending motion of screws itself up. Y

The device so far described is not essentiall diierent from known constructions. feature resides in the manner wherein spring I4 cooperates with nut I3 and. handwheel I5. As

illustrated, said spring is confined between the Its noveli i bearing I'Ia, exerts an upwardly directed pressure on the nut, whereby thebit 2 is relieved from pressure.

f Fig. 2 shows a second embodiment of the invention. In accordance with this gure, the spring .member is constituted by two aligned coiled 'springs Ida, I4, and the two abutments of the handwheel (viz. that for the bottom end of spring |48 and that for the top end of the spring Mb) upper and the lower race, respectively, of two ball `v bearings II and Il, which are axially slidable with their inner cylindrical faces on the outer i V wall of a reduced portion of nut I3, and with their outer cylindrical faces on the inner y wall of a turned out portion of hub I6, it being, understood that the shoulders confining said reducedl and" A' turned out portions constitute the abutments referred to hereinbefore.

If handwheel I5 assumes a low position, ball bearing I'I engages'the bottom abutment of nut I3 and the top abutment of the `handwheel engages ball bearing' I'Ia, so that tensioned spring I4 exerts pressure on nut I3. This pressure may be increased by handwheel I5 being. screwed still further down, If the handwheel is screwed upward through a certain distance, the ball bearing Ila will engage theV upper abutment of nut I3, while ball bearing II still engages the lower abutment of said nut, and under these conditions the spring load in the nut is nil. Further upward movement of the handwheel will cause ball bearing VI to disengage the lower abutment of the nut, the consequence being that the spring, through the ball are formed'by the top face and the bottom face, respectively, of a circular shoulder IIa on the inner wall of hub I6.

What I claim is:

A rotary drill conprising, in addition to a bit secured to a threaded rotary stem engaged by a nutadapted to be rotated by the stem at a speed diieri'rig from that of the stem so that the stem is automatically screwed upward when the nut is arrested, a clutch in the transmission gear between stem and nut and adapted under the influence of the descending stem automatically to be thrown in'to turn the nut in accordance with the descending motion of the stem, and a spring member encircling the stem and bearing with its bottom end against an abutment of the nut, said spring member bearing with its top end against an abutment of a tensioning member having a threaded hubV adapted to be screwed up and down in a stationary casing accommodating the nut and the clutch, wherein the nut is also provided with an abutment for the top end, and the tensioning member is also provided with an abutment for the bottom end of the spring member, or ofpart of said spring member.

CORNELIS J. ESSELING. 

